Latex composition and its preparation



UNITED STATES PATENT OFFICE LATEX COMPOSITION AND rrs rnarannrron Milton 0. Schur, Berlin, N. 11., amino:- to Brown gitgpany, Berlin, N. 11., a corporation of No Drawing. Application September 4, 1931, Serial No. 561,256

2 Claims. (Cl. 134-17) The subject of this invention is the preparaings, stretchings, or other mechanical stresses. tion of latex compositions, and more particularly In these latter instances, the artificial leather ones commingled or blended with aqueous dismay fail in a comparatively short time. persions of other materials, such compositions be- The anti-oxidants to which I have adverted 6 ing intended for various uses, for instance, as the need not necessarily be of a waxy consistency, but impregnants of bibulous fibrous foundations in there are some which are highly desirable for use the production of artificial leathers or the like. in making artificial leathers and which happen There are certain bodies which can be incorpoto be of a waxy nature. For instance, one antirated into solid or coagulated rubber with relaoxidant available on the open market and sold 10 tive ease by the usual procedure of compounding under the trade name of AgeRite Gel is a waxy 5 on a roll mill or in an internal rubber-mixer. material consisting of a mixture of ditolylamines Thus, waxy, greasy, and oily bodies lend themand a special petroleum wax. This anti-oxidant selves to such compounding with solid or coaguis eminently adapted for use along with waterlated rubber. On the other hand, it may be a dispersed rubber in making artificial leathers of matter of considerable difiiculty to disseminate the type described, not only because the anti- 70 bodies of this character uniformly throughout oxidant retards the deteriorating influence of the aqueous dispersions like rubber latex or artificial atmosphere, but also because it imparts to the aqueous rubber dispersions. Some of the so-called artificial leather an enduring pliancy and melanti-oxidants sold on the market are of a waxy lowness highly desired. This anti-oxidant is furnature and are resistant to direct dispersion in ther a highly desirable one, in that of all the 75 water even in the presence of certain well-known powerful anti-oxidants commercially available, hydrophilic colloidal dispersing agents of the nait is the one which causes the least discoloration ture of soaps. While it may be possible to disor staining, particularly on exposure to sunlight, perse such wax-like anti-oxidants under special when the leather is surface-finished as with the conditions, i. e., with the use of particular hydrousual nitrocellulose lacquers. 8o philic colloids, temperature conditions, and appa- I have found that waxy anti-oxidants, and more ratus, nevertheless I have found a positive, simple especially AgeRite Gel, can be brought into fine and inexpensive procedure of getting wax-like dispersionin water by an indirect procedure based anti-oxidants or analogous bodies into aqueous on an initial absorption of the same by a finely dispersions of a high order of stability and lendpulverulent carrier preserved substantially as 85 ing themselves to easy blending with other aquesuch. The finely pulverulent carrier containing ous dispersions, e. g., rubber latex or artificial the anti-oxidant distributed therethrough in abaqueous rubber dispersions. The dispersion of sorbed condition may then be readily dispersed wax-like anti-oxidants in water is a matter of in water preferably containing the usual hydroparamount importance, on account of the fact philic colloids. Indeed, the finely pulverulent 90 that suchadispersiorrmaybeblended with rubber carrier may be one which it is desired to comlatex to produce a composition having those qualpound with the rubber anyway, for latex or aqueities requisite for the impregnation-of bibulous fious rubber dispersions are commonly used along brous foundations in the manufacture of artificial with powdered zinc oxide, lithopone, litharge, or

leathers. For some time, it has been known that like rubber-compounding agents. In such case, 5 artificial leathers can be produced by starting all that is necessary is to cause the absorption by with a bibulous fibrous foundation, e. g., one made the powdered rubber-compounding agent of the up of loosely interfelted wood pulp, impregnating anti-oxidant, whereupon the mixture may be dissuch a foundation with rubber latex, and then persed in water and the water-dispersion ad- 00 removing the water by drying so as to cause a, mixed with rubber latex or artificial aqueous rub coalescence of the rubber particles and a conber dispersion. This sort of procedure has been comitant. tenacious bonding of the fibers. One" found to work perfectly when powdered zinc oxof the troubles which is apt to arise in connecide, for example, is used as the absorbent carrier tion. with artificial leathers so made is their or base and as the rubber-compounding agent. 105

deterioration under oxidizing influences, as when I shall, therefore, now give an exemplary procemerely exposed to the atmosphere. In some indure in which zinc oxide serves these functions. stances, this deterioration may not be serious, but To about 5 parts by weight of zinc oxide in the it is of great moment when the artificial leatherv form of dry powder sold under the trade name is put to use as shoe uppers or in other connecof Black Label Kadox may be added 1 part by no tions where the leather undergoes repeated fiexweight of the waxy AgeRite Gel. The batch may be mechanically mixed, during which operation the wax-like material gradually disappears throughout the powder,so much so that the thoroughly mixed batch no longer contains observably free anti-oxidant and is characterized by a dry appearance and a free-flowing quality. By this, I mean that although at the start of the mixing operation the mass may be locally dough-like, nevertheless as the mixing operation continues and the anti-oxidant is distributed through the powder, the particles of zinc oxide again become substantially individualized and can be said to have reverted, to their original pulverulent state. then be transferred to a ball mill and water may be added thereto during the operation of the mill in amount sufiicient to produce a paste or flowable aqueous suspensiomat which stage a slight amount of a suitable hydrophilic colloid, e. g., a mixture of. ammonium caseinate and gelatine, is preferably added thereto. The operation of the ball mill may be continued until a uniform aqueous dispersion of the mixture has been attained, which result may be had in about an hour or two. Surprisingly enough, the aqueous dispersion thus produced manifests no greasiness whatever, indicating that the anti-oxidant has been very finely dispersed. This dispersion is also remarkably stable in that there is no tendency for greasy particles to become apparent therein over long periods of time. This dispersion, containing, say, 3 parts of water to 1 part of dispersed solids, is ready for comminglingwith rubber latex in the desired proportions. A typical blend of the dispersion with latex may be made to contain, say, 5% zinc oxide, based on the rubber content of the blend, which would also contain 1% antioxidant, based on rubber. The blend may also contain, say, 1 /z% colloidally dispersed sulphur, based on rubber, and, say, of an ultra accelerator of vulcanization like "Pipsol-X, based on rubber. The sulphur and accelerator of vulcanization may, of course, be incorporated into the rubber latex prior to blending with the waterdispersed mixture of zinc oxide and anti-oxidant. The blend or latex composition thus produced may serve as the impregnant for bibulous fibrous foundations in the production of artificial leathers. For example, a web of loosely-formed wood pulp made on machinery of the papermaking type may be dipped into a blend or latex composition such as described, at a solids content of about 20%, under which conditions rapid impregnation of the web ensues.

The impregnated web may then be dried at elevated temperature to coagulate the rubber and to vulcanize the product. The leather-like product can be surface-finished, as with nitrocellulose lacquer, and embossed to simulate the grain effects of natural leather. The finished leather possesses enhanced stability and resistance'to deterioration by virtue of its content of anti-oxidant' intimately associated with the rubber throughout the leather. As already indicated, the anti-oxidant also imparts thereto a degree of pliancy or mellowness, which makes easier the lasting and pulling-over operations when the leather is used in shoe uppers. The shoes in which such artificial leather serves as. the upper are more comfortable to the wearer, being possessed of the appropriate feel and softness to the foot. In the example cited, the fibrous foundation, after having undergone impregnation in the latex composition, is preferably squeezed to a rubber content of about 100%. based on the weight The powdered mixture may of dry fiber, as this makes for a finished product having those characteristics desired in shoe uppers. v

The latex composition prepared in accordance with my invention may also be used in making dipped rubber goods, as a coating material, in the treatment of textile cords for tire manufacture, in the impregnation of other than fibrous foundations,. and in the impregnation of fibrous foundations to produce artificial leathers intended for use as inner soles, outer soles, automobile topping, upholstery fabrics, belting, and other ultimate products.

The principles of the present invention can be applied in making water-dispersions of waxy, greasy, and oily bodies, irrespective of whether or not. such bodies are anti-oxidants in character and whether or not the dispersions are to be admixed with latex or other dispersionsof waterimmiscibles bodies. The dispersed waxy, greasy and oily body may have application as a sizing for fabrics or the like, in which case the powdered material serves not only as a carrier for the water-repellent material, but as a filler or loading ingredient. The water-repellent material may function to impart water-resisting qualities to the fabric to which it is applied. So far as I now know, however, the greatest utility of my invention lies in the possibility of dispersing waxy bodies, preferably of an anti-oxidant nature, in water along with finely powdered rubber-compounding agents, to produce an aqueous dispersion valuable for blending or compounding with rubber latex or artificial aqueous rubber dispersions in manufacturing goods of the class hereinbefore described. In all instances where my invention is applied, the initial step of making the powdered material serve as the carrier for the water-immiscible, waxy, greasy, or oily body is conducted under conditions conducive to a maintenance of the powdered material in substantially dry condition, enabling dispersion in water with no observably free water-immiscible body. While the most stable dispersions are realized by adding a hydrophilic colloid to the water in which the powdered carrier for the waxy, greasy, or oily body is dispersed, nevertheless, a fine suspension of the carrier and the waxy, oily, or greasy substance may be had in water alone. I prefer, however, to use a protective colloid in the water so as to avoid separation of the carrier and the waxy, greasy, or oily body.

Just to show another instance of valuable application of the principles of the present invention, I shall describe how ozokerite or ceresin was dispersed in water and in such condition blended with latex. Both these bodies are considered to be dimcultly dispersible in water, but no trouble whatever was experienced in dispersing them according to my method. Ozokerite, which is a comparatively hard wax related more or less to petroleum wax, is considered to act not only as a softening agent for rubber, but also somewhat as a preservative. I observed that this wax, because of its comparatively hard nature, worked into a pulverulent carrier like zinc oxide powder with a little more than usual difiiculty. Al-' though matters might have been helped by warming the wax, the zinc oxide, and/or the container in which they were mixed, I found it more convenient to treat the wax-with a small amount of volatile softener or solvent like carbon tetrachloride, which could easily be removed by evaporation after the softened wax had been intimately mixed with the powdered carrier. Specifically the procedure may be about as follows: Ozokerite or ceresin may be softened by the addition of a little carbon tetrachloride. It may then be readily admixed with about five times its weight of finely divided zinc oxide. The mixture may then be allowed to remain exposed to the atmosphere until the carbon tetrachloride has been substantially completely volatilized. The resulting dry, free-flowing powder may be transferred to a ball-mill wherein it may be ground in the presence of water containing a small amount of hydrophilic colloid, for example, ammonium caseinate and/or gelatine. After an an hour or two, the mixture will be colloidally dispersed in the water. The aqueous dispersion may now be added to rubber latex in proportion to yield a mixture containing 20% rubber, 5% zinc oxide, 1% ozokerite, 3% sulphur and Pipsol X, all based on rubber. The mixed dispersion may advantageously be used for the impregnation of bibulous fibrous webs, which, upon drying, are transformed into soft, pliable sheets having leather-like qualities. The use of carbon tetrachloride or equivalent volatile softener or solvent facilitates the distribution of the waxy exposure of the mixture to the atmosphere. Or, it may be found more convenient to dissolve the waxy body completely in a volatile solvent, whereupon the pulverulent carrier may be added tothe solution to form a thin or fluent slurry or cream. The solvent may then be evaporated, with the application of heat, if desired, to hasten evaping agent of the character of zinc oxide carrying a mixture of ditolylamines and petroleum wax.

2. A process which comprises mixing about 5 parts by weight of powdered, rubber-compounding agent and about 1 part by weight of a mixture of ditolylamines' and petroleum wax until the resulting mixture has a free-flowing quality, dispersing the resulting mixture in water in the presence of a protective colloid, and blending the ozokerite uniformly throughout the pulverulent aqueous dispersion with an aqueous rubber discarrier; and in the event that the presence of the solvent in the final dispersion is undesirable, it can be removed, as already described, by mere persion of the nature of latex.

MILTON SCHUR. 

